Fabrication and Characterization of ZnO Films by Electrophoretic Deposition

The electrophoretic deposition (EPD) of flakelike nanoparticles was investigated, and reticular ZnO films with porous nanocrystal plates were fabricated on tin doped indium oxide (ITO) coated glass substrates. The effect of processing parameters including current density and deposition time on surface morphology and phase composition of ZnO precursor films were examined. The results show that these nanoplates cover the substrate horizontally at a low current density, and will vertically arrange on the substrates to form uniformly distributed reticular film at a high current density. A possible formation mechanism is assumed based on the distribution of electric charges on the surface of these nanoplates. Increasing deposition time might attribute the formation of flowerlike microscale spheres due to the assembly of some nanoplates. The deposited films from colloidal suspensions mainly consist of two phases of ZnO and Zn₄CO₃(OH)₆H₂O, and then Zn₄CO₃(OH)₆H₂O phase in the films will be transformed into ZnO completely after heat-treatment. The formation of porous nanoplates might be attributed to the release of water and CO₂ from the decomposition of Zn₄CO₃(OH)₆H₂O phase. Micro and nanometer hierarchical structures of ZnO films are enhanced by heat treatment.